Colored vulcanized rubber and process of making the same



Mar. 20, 1928.

1,663,436 PATENT OFFICE.

ERNEST B. BRIDGWATER, OF WILMIIlGTON, DELAWARE, ASSIGNOR TO E. I. DU PON'I' 10E NEMQUBS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DEL- AWARE.

COLORED WLCdNIZED RUBBER AND PROCESS OF MAKING THE SAME.

No Drawing".

This invention relates to the coloring of rubber, particularly in orange and red shades.

Une object of my invention is to provide a coloring matter for rubber which can be used in relatively small proportions to produce a very brightly colored rubber.

Another object of my invention is to provide a coloring matter for rubber which will have no tendency to retard the vulcani- .zation thereof, and which will have no other deleterious eflect on the quality of the rubber compound.

It has been known for several years that the lakes made from the heavy metal salts of the compound. produced by coupling diazotized Q-chlor-5-toluidine-4-sulfonic acid with beta-naphthol could be used for coloring rubber which was vulcanized by heat. These heavy metal lakes produce a fairly satisfactory color in rubber but must be used in relatively large amounts, in order to produce a certain brightness of color. I have now discovered that the alkali-metal salts of the compound produced by coupling diazotized 2-chlor-5-toluidinel-sulfonic acid with beta-naphthol produces. brighter colored rubber than the previously known compounds. Rubber containing colors of this group is not subject to bleeding or blooming of the color and retains its brightness and desirable physical properties very well during storage and in service. The alkali-metal salts of the compound produced by coupling diazotized 2-chl0r-6-toluidine-4-sulfonic acid with beta-naphthol have similar properties and produce similar results in rubber compounds.

The following is an example of the use in rubber of the sodium salt of diazotized 2-chlor-5-toluidine-4-sulfonic acid coupled with beta-naphthol:

This compound should be vulcanized for 40 minutes at 40 pounds steam pressure. Any other organic accelerator which does hpplicatien filed January 29, 1926. Serial No. 84,783.

mula

1. The process of coloring rubber which I comprises mixing rubber or rubber-like materials with a vulcanizing agent and with the sodium salt of the azo compound 0btainable by coupling diazotized 2-chloro-5- toluidinel-sulfonic acid with beta-naphthol.

2. A colored vulcanized rubber obtainable by mixing rubber or a rubber-like material with an azo sodium sulfonate having the following graphical formula:

O Na

and with a vulcanizing agent, and other compounding ingredients and vulcanizing the mixture.

3. A vulcanized rubber product having a color ranging from red to orange-red, and characterized by containing a coloring matfillers, and

ter having the following general formula: where the azo group is attached to the 5 or 6 posit-ion of the benzene ring, and where M 10 represents an alkali-metal.

, In testimony whereof I aifix my signach H ture.

ERNEST R. BRIDGWATER'. 

